1. Technical Field
The present disclosure relates to an impact absorber for absorbing collision impact.
2. Description of the Related Art
In recent years, strengthening of a car body and mounting of an air bag have been implemented to enhance collision safety performance of a car. In addition, reduction in fuel consumption has given much consideration for resource saving, environmental issues, for example. Thus, the inventors have found that reduction in weight of a car has been strongly demanded. Therefore, materials of various components in a car have been expeditiously converted from metal materials to resin materials, while reduction in amount of a resin material used in a component has been also rapidly progressed.
In recent years, moreover, enhancement in safety performance in a lateral collision has been also explored in addition to improvement in safety performance in a head-on collision. The door enhances the safety performance in the lateral collision. For this reason, an impact absorber for relieving an impact on a car in a lateral collision is placed between a door panel and a door trim.
Exemplary impact absorbers include, for example, one having a hollow wall structure formed by blow-molding a thermoplastic resin. For example, an impact absorber disclosed in Japanese Patent No. 3313999 has a body in the form of an almost hollow cube. The body is provided with an abutting surface and a support surface that are opposed to each other. The abutting surface has a recessed rib formed by denting a part thereof toward the support surface. Moreover, the support surface has also a recessed rib formed by denting a part thereof toward the abutting surface. Moreover, there is disclosed an impact absorber constituted to have a bonding portion on which tips of two recessed ribs abut.
In the lateral collision, a passenger hits the door trim. At this time, an impact to the passenger is relieved by the impact absorber provided in the door trim. Consequently, the passenger is protected.
In some cases in which an impact speed is high, however, a waist portion of the passenger hits the door trim. In these cases, a great load is applied to the waist portion of the passenger through the door trim. The great load affects the passenger in some cases. For this reason, attempts are made to reduce the load to be applied to the passenger in a collision.
There is a document (for example, JP-A-2004-299632), which discloses a structure of a door trim for a vehicle to achieve a high impact-absorbing property. The structure of a door trim for a vehicle described in JP-A-2004-299632 includes a portion that corresponds to a soft abdominal portion of a passenger and has a low impact-absorbing property. On the other hand, the impact absorber has a high compressive strength in a portion corresponding to a comparatively hard waist portion.
In the structure of a door trim for a vehicle which is disclosed in JP-A-2004-299632, a plurality of recessed ribs 8 is formed to absorb an impact. An interval between an external wall surface 5 and the tip portion of the recessed rib 8 is 20 to 40 mm in a portion “a” corresponding to the abdominal part of the passenger. On the other hand, both the external wall surface 5 and the tip portion of the recessed rib 8 are close to each other, abut on each other or are welded to each other in such a manner that the interval between them is smaller than 20 mm in a portion “b” corresponding to a waist portion of the passenger.